It must first be addressed that under UK law, you can "self certify" for up to 5 working7 days. This means you call in sick and you diagnose yourself. Anything above that requires a doctors note. It also means that, in reality, unless you're under a review specifically about your attendance, they're not supposed to accuse you of being anything other than ill.
The return to work interview is standard practice. It's more to cover their backs than it is yours, as they will record your absence and review it during yearly employment reviews.
5 days sick in a year isn't high. 5 occurrences of being off work sick is high. It's a subtle difference in the way HR have worded it, but I would assume they've used the Bradford Factor when calculating your time off.
The Bradford Factor is a simple formula used by employers to calculate how much time, in reality, an employee has off. Your "BF" is calculated by:
- (Number of occasions sick)2 x Total number of days absent
In your case you say you've had 5 sick days off in a year. But you also mention that that's over 4 occasions. So if we calculate your time off as so:
- 42 x 5
That gives you a score of 80. Under the Bradford Factor this is considered normal.
However, if you had 5 days off on 5 separate occasions, your score would be 125 which is considered high.
In the UK there is an expectation that unless your leg is falling off you should be in work. I don't agree with that, and if I have a cold where I'm constantly coughing or tired I will not go to work. If work is particularly bad, I will work from home. But, as far as I am concerned, I am putting others at risk of catching an illness which could and would incur a number of colleagues falling ill. This also goes for sickness and diarrhea, as the bugs that cause these are extremely contagious. Which is a concern especially if a member of your team is pregnant.
I too am a software developer and can emphasize with you on your description of being ill while working. I've worked in many industries, in many offices, for many different people, and having a day off because of the flu has never been an issue.